1. Field of the Invention
This invention relates to drivers that include power transistors. More particularly, this invention relates to a high-side, low-side configurable driver for inductive and/or resistive loads that is capable of handling fault conditions and dissipating inductive energy during the fault conditions.
2. Background Information
Automotive applications typically require the switching of loads such as lamps and/or inductive solenoids. The loads are generally connected to a driver or switch in either a high-side or a low-side configuration. In the high-side configuration, the load is connected between the driver and ground. In the low-side configuration, the load is connected between a voltage source and the driver.
Multiple driver circuits are often combined into an integrated circuit module. The module, in turn, is connected to the battery of the vehicle and ground. A microprocessor is typically associated with the driver and is connected locally. The loads are generally connected remotely.
The module detects and reports open and shorted loads, provides thermal protection, survives loss of module ground, and survives reverse battery faults. The module must also protect against supply interruption during energized inductive loads and comply with other transient tests. While many conventional modules are capable of providing these features, the modules typically require the addition of external components which diminish the reliability of the electronic system, add to the overall cost, and increase the overall size of system
Conventional modules that address the reverse battery and partial loss of ground issues employ either blocking field effect transistors (FETs), blocking diodes, or isolated substrates. These solutions are complex, costly to manufacture, tend to reduce the overall system reliability, and/or degrade the performance of the module. By placing a diode in series with the drain of the FET, the device is protected from the reverse battery fault condition. The voltage drop across the diode, however, degrades system performance. In addition, the diode cannot be realized in an integrated circuit in a standard plastic package due to thermal dissipation and size issues. Therefore, discrete elements must be added to the integrated circuit.
The power transistor may also be protected by a second power transistor which is coupled upside-down and enhanced during normal operation with a charge pump. This technique is disclosed in U.S. Pat. No. 5,434,739, which is hereby incorporated by reference. None of these conventional solutions address the loss of ground.